1. Field of the Invention
The various embodiments of the invention are directed to determining the statistical reliability of a device or group of devices, such as a logging tool. More particularly, the various embodiments of the invention are directed to predicting reliability and/or updating reliability prediction models for downhole devices.
2. Background of the Invention
In drilling boreholes into hydrocarbon-producing reservoirs, it has become commonplace to include in a drill string one or more logging tools. There may be a vast array of combinations of logging-while-drilling (LWD) and measuring-while-drilling (MWD) tools that may be placed within a drillstring, but these tools generally comprise mechanical apparatuses and electrical circuits to perform specific tasks. The time-to-failure of these mechanical and electrical devices may be related to the conditions in which they operate.
The operating environment experienced by downhole devices is very harsh. By virtue of the devices being part of the drillstring, the devices experience relatively high accelerating forces, which may be caused by vibration of the drill bit cutting through the downhole formations. The devices may also experience temperatures far in excess of normal surface conditions. The temperature and vibration experienced may exceed the specified ranges for some of the components that make up the downhole devices, such as electrical components. Thus, the life span of any particular electrical and mechanical device may be related to the amount of time that device operates within high temperature and high vibration environments.
While it may be known that the life span of electrical and mechanical devices may be proportional to operating temperature and vibration experienced, there has not been a mechanism where this information may be tracked real-time or predicted so as to quantify the statistical reliability of a particular tool or downhole assembly.